1. Field of the Invention
The present invention relates to a tracking control circuit for use in a composite digital VTR (video tape recorder) or the like, and more particularly to a control circuit for tracking in an edit mode.
2. Description of the Prior Art
It is generally customary that tracking control in a recording apparatus such as a VTR is performed on the basis of a reproduced envelope signal which represents the amplitude of a reproduced output from a playback head. However, since the reproduced envelope signal may vary widely depending on the recorded contents, it is impossible to employ such tracking control means in cases where the level variations of the reproduced envelope signal adversely affect tracking control precision.
In executing an insert edit for example, it is necessary to perform edit tracking control which eliminates any positional deviation between a track to be newly recorded and a base track by adjusting the recording head to the base track instead of adjusting the tracking of the playback head. In such edit tracking control, if there is even a slight variation in the level of the reproduced envelope signal, the recording head will fail to follow the base track properly unless the phase of a control signal CTL is adjusted in compliance with such variation.
Therefore it is impossible to achieve proper tracking control in an edit mode by using a reproduced envelope signal whose amplitude level varies depending on the recorded contents.
In an attempt to solve this problem, it has been usual heretofore to adopt a method involving an equivalent circuit in a playback system to reduce level variations of the reproduced envelope signal, or a method involving the prior recording of a pilot signal or the like to obtain a fixed playback level.
However, there are difficulties in effectively suppressing level variations in the reproduced envelope signal by use of an equivalent circuit to minimize the level variation. Another unavoidable disadvantage is the complicated nature of the circuit configuration. Even using the superimposed pilot signal method, the problem of complicating the circuit configuration still remains unsolved since a particular recording/playback system is required.